Advice on Ox sensor codes and whether Catalytic converter(s) could need replacing

[TurnAround]

2003, 3.0i M54, 117,000 miles, PowerChip ECU remap is only mod



2 weeks ago the SES light came on. Checked codes with my Peak Research R5. Rest them. Same exact set came back within 5 miles. Reset again. Same codes again soon after. Summary of what I got:

• • Misfire on all cylinders
  • 02 Sensor Adaptation Limit, Cyl 1-3
  • 02 Sensor Adaptation Limit, Cyl 4-6
  • 02 Sensor Control Limit, Cyl 1-3
  • Catalytic Converter Efficiency, Cly 1-3

From this list, I couldn't tell a difference between upstream 02 sensors, and downstream. Just the bank difference.

After researching this board I decided that I would just replace all four 02 sensors, since the car has 117k and the sensors are designed for ~100k. I could have done upstream and waited, but I drive the car on long trips and don't want to risk stranding or long drives with SES light on. I paid my indi to do it. I own two other M54s and the next one that needs them, I'll probly do the upstream 02 sensors myself. Anyway, they replaced them Dec 31st, and I ask them not to read the codes and just do the replacement... because they charge $90 to diagnose, and I like to skip that step when I can if my Peak tool is uber clear on the codes.

When I got the car back it was still running rough, which surprised me. SES came on shortly there after, and the same codes came up again. Oye.. Reset, and then they came up again. Crap.

So the sensors and labor are under warranty, but, now I've been researching catalytic converter issues on this board. I'm going to be shitlessly bummed if my cats are bad, due to the unbelievable cost of those things, plus labor. The car goes back in on Monday Jan 5, and this time I feel I don't have a choice but to let them fully diagnose it, but.. I want to arm myself with the max information before going in, because I'm reading here that several of you have had similar issues, and the subsequent diagnosis was long and drawn out.

I'm having them replace the fuel filter (just for similar preventative reasons.. save the fuel pump). Mentioning, just in case its related.

Spark plugs were replaced the other day, along with the 02 sensors.

I'm reading it could be the cam shaft sensor(s). Got it, understood. I've replaced those on my other two Z's (Though I'm not getting those codes on the X).

I hear that it could be the vaccum system, or a manifold leak, or maybe even a gas cap. Got it.

Any other advice? Thanks!

[upallnight]

You need to look at other things other then just the trouble codes. It would have been also nice if you gave the actual trouble codes in your post. I would have looked (there's an APP for this) at the short term and long term fuel trim and the voltages that the 02 sensors were putting out before replacing parts. Could be a dirty MAF or a bad MAF. Rough running is probably attributed to injectors shut down by the DME when it detected the misfires.

How long have this situation been going on? Running with a rich engine could destroy a cat in no time.

[TurnAround]

Since Christmas Day.. visiting folks a ways away. Total miles since rough idle and codes showed up; 160 miles. The car goes in Monday. I'll avoid driving it.

I can look up the codes from my Peak Research booklet, but I got the impression that they're just 2 letter/digit codes that are proprietary to Peak. Their format doesn't match the codes I see you guys reporting. You're saying there's an app to convert Peak's codes to standard notation codes?

I've had MAF problems in the past, which, always trigger a TRANS FAILSAFE PROG. The MAF has been replaced twice in the past. Then, the last time it happened this summer (112k miles) I learned from this board to clean the existing MAF with hexane spray. That did the trick. I now keep a can of Hexane spray in the stow hold in back. Would cleaning the MAF now with hexane possibly clear the problem?

Thanks for replying btw!

[upallnight]

I said that there's an app to read real time data from the engine while it is running. I use Torque Pro with a Bluetooth module plugged into the OBD II connector. You need to select the data that you want to see while running the app. The non pro app is for free on Google play.

I have used MAF cleaner by CRC to clean the MAF on my BMW. I have also replaced the MAF on the BMW after trying to clean it didn't work. If you do have a bad MAF, don't buy one of those cheap one on Amazon or eBay. Get a Siemens MAF.

[TurnAround]

Ah, now I get it. Yeah, a guy at work was telling me he had something similar. Ok, looks like its time to abandon my Peak code reader and change up to app driven readers. Thanks.

I took it in today. For this issue, at this point (need the car back, daily driver) its now in my indi techs hands to fully diagnose. Crossing my fingers that its not the catalytic converters. I went through the list with them of other things to run down.

THanks for your help. I'll post back when we have a fresher diagnosis.

[bcredliner]

Hardly ever good to throw parts at an issue before all troubleshooting and diagnosis has been exhausted. I think the $90 would be well spent.

There are many potential causes that are upstream from convertors and O2 sensors that will cause O2 sensors and cat errors when they are fine. Post cat 02 sensors are primary for emissions and are very unlikely to cause a rough idle.